Electronic supplementary material
The online version of this article (doi:10.1186/1472-6963-12-270) contains supplementary material, which is available to authorized users.
The authors declare that they have no competing interests.
JM participated in the study design, performed the data management and statistical analyses, and drafted the manuscript, tables and figures. EK and TH designed the primary study data collection  from which the analytic datasets for this manuscript were obtained, provided guidance to JM in the data analysis and interpretation, and design and interpretation of the study presented in this manuscript and provided significant edits to this manuscript. MH provided expertise on interpretation of the refill measure based on prior work  and provided significant edits to the manuscript. All authors read and approved the final manuscript.
Many patients have uncontrolled blood pressure (BP) because they are not taking medications as prescribed. Providers may have difficulty accurately assessing adherence. Providers need to assess medication adherence to decide whether to address uncontrolled BP by improving adherence to the current prescribed regimen or by intensifying the BP treatment regimen by increasing doses or adding more medications.
We examined how provider assessments of adherence with antihypertensive medications compared with refill records, and how providers’ assessments were associated with decisions to intensify medications for uncontrolled BP. We studied a cross-sectional cohort of 1169 veterans with diabetes presenting with BP ≥140/90 to 92 primary care providers at 9 Veterans Affairs (VA) facilities from February 2005 to March 2006. Using VA pharmacy records, we utilized a continuous multiple-interval measure of medication gaps (CMG) to assess the proportion of time in prior year that patient did not possess the prescribed medications; CMG ≥20% is considered clinically significant non-adherence. Providers answered post-visit Likert-scale questions regarding their assessment of patient adherence to BP medications. The BP regimen was considered intensified if medication was added or increased without stopping or decreasing another medication.
1064 patients were receiving antihypertensive medication regularly from the VA; the mean CMG was 11.3%. Adherence assessments by providers correlated poorly with refill history. 211 (20%) patients did not have BP medication available for ≥ 20% of days; providers characterized 79 (37%) of these 211 patients as having significant non-adherence, and intensified medications for 97 (46%). Providers intensified BP medications for 451 (42%) patients, similarly whether assessed by provider as having significant non-adherence (44%) or not (43%).
Providers recognized non-adherence for less than half of patients whose pharmacy records indicated significant refill gaps, and often intensified BP medications even when suspected serious non-adherence. Making an objective measure of adherence such as the CMG available during visits may help providers recognize non-adherence to inform prescribing decisions.